LAUSANNE, Switzerland — Colorful placards in the Olympic Park here, the home of the International Olympic Committee, detail cultural, architectural and environmental trivia about Brazil, the site of this summer’s Olympics. Introducing Rio de Janeiro as home to 41,000 plant species and the biggest urban rain forest in the world, the placards advertise “all you need to know about the Rio Games before you even get there.”
But some timely facts are missing: Brazil is in the midst of a deepening financial crisis. The country has also been hit hard by the Zika virus, an international outbreak that the World Health Organization last month declared a public health emergency.
On Wednesday, officials of the International Olympic Committee gathered here in closed-door meetings to discuss the virus’s impact on the games, along with the other concerns Rio faces as its seeks to deliver on the promises it made in 2009 that established it as the first South American city to host an Olympics.
In a conference room at the Lausanne Palace Hotel, Carlos Arthur Nuzman, the president of the organizing committee for the Rio Games, delivered updates to Olympics executives, with Rio’s mayor connected by telephone. The discussion included the mosquito-borne Zika virus, venue logistics, budget details, transportation projects and sluggish ticket sales.
With just five months left before the Games are scheduled to begin, Rio Olympics organizers are trying to tamp down escalating concerns on several fronts, including the growing belief that fears around Zika will greatly diminish attendance and stir anxiety among athletes.
“We had less questions than the last one,” Mr. Nuzman said after the meeting, which had extended beyond the executives’ appointed lunch hour. “A little long, we know, but we have five months to go. We needed to present.”
Mr. Nuzman said ticket sales had “increased a lot.” He reported to officials that 47 percent of tickets to the games had been sold, generating $194 million in revenue.
“This worldwide mosquito — the executive director of the World Health Organization recognized it has no problems,” Mr. Nuzman said, referring to Dr. Margaret Chan, the director general of the W.H.O., who visited Brazil last month and met with the country’s president.
Dr. Chan has called for “a coordinated international response,” but the W.H.O. has not recommended travel restrictions.
Last week, however, the Centers for Disease Control and Prevention in the United States advised pregnant women not to attend the Rio Olympics because of the Zika virus and its possible relation to birth defects.
It is unprecedented for a federal agency to counsel a specific group not to attend an Olympics for health reasons, said Martin Polley, a sports historian specializing in the Games who teaches at De Montfort University in England.
“Particular populations have been advised not to go to the Olympics on political grounds,” Mr. Polley said, citing the 1936 games in Berlin, “but public health is a different matter.”
When asked Wednesday about the CDC advisory, Thomas Bach, president of the International Olympic Committee, said, “Our partner is the World Health Organization, and we rely on this partnership and this cooperation and on the advice of the World Health Organization.”
Mr. Bach said that local authorities were vigilantly monitoring for standing water, to minimize mosquito breeding, and that he was pleased that air conditioning would be installed in the Olympic Village, in place of using open windows to ventilate rooms and risk mosquito entry.
The Zika virus is not known to be fatal but has been linked to temporary paralysis and microcephaly, a condition in which infants are born with small heads and brain damage. As many as 1.5 million people in Brazil are believed to have contracted the virus, which is also possibly transmitted through sexual contact, and which researchers have suggested arrived in the country during another major sporting event: the 2014 World Cup.
With some 500,000 people expected to descend on Rio this summer, the Olympics could significantly advance Zika’s spread around the world, experts have warned.
There is no reliable test yet for the virus, but the World Health Organization said last month that scientists were “weeks, not years” away from developing one, while forecasting that clinical trials for a potential vaccine would not begin until at least August 2017.
Even so, infectious disease is not the only concern as the games approach. Rio is grappling with infrastructure issues, political unrest and financial instability, which could jeopardize the organizers’ grandest plans to present the city’s best face to the world.
Mario Andrada, a spokesman for the Rio organizing committee, said there had been “impressive” financial cuts to the Olympic budget, but that none would affect the experience of athletes competing at the games.
A basic topic of the executives’ discussion on Wednesday was a stalled public transportation project — an extended subway line that would link the Olympic Park with the rest of the city — that had been a critical promise in Rio’s bid.
Mr. Nuzman said he had assured officials that the subway would be up and running in time.
“It seems like there’s a perfect storm brewing,” said Scott Kirkpatrick of Chicago Sports and Entertainment Partners, a sports marketing consulting firm. “The Brazilian financial crisis, impeachment proceedings against the president, the Zika virus — there’s a lot going on.”
Mr. Kirkpatrick, who played a role in Chicago’s bid for the 2016 Olympics, called Rio’s concerns “real and legitimate,” but noted that panicked reactions leading up to the Athens Games in 2004, Beijing in 2008 and Sochi in 2014 had proved unfounded, a point Mr. Nuzman also made on Wednesday.
Ultimately, Mr. Kirkpatrick said, he believed the games would be carried off without incident, even if attendance was lower and some venues sat partially empty during competition, as they did at the Athens Games.
The International Olympic Committee has made clear that it is committed to Rio as this summer’s host and has expressed steady confidence that the games will be carried off.
“Considering the enormous amount of planning that goes into an Olympics, there simply cannot be a contingency,” Mr. Polley, the sports historian, said. “The coordination of central and local government, sponsors, broadcasters. The logistics are too many.”
Much must still be done to prepare. Downhill from the Olympic Park here, at the water’s edge, an Omega-branded digital clock counts down to the Games, reminding officials they have little more than 150 days until the Aug. 5 opening ceremony.
Athletes from around the world have already begun competing in Rio for test events, which had taken place without delay, presenters noted on Wednesday. Synchronized swimmers and women’s rugby players are scheduled to compete there this week.
Like the International Olympics Committee, sports federations and national organizing committees have projected confidence about the games, saying little beyond assuring their constant review of the situation.
The United States wrestling team competed in Rio in late January. “The women were there, they wrestled well and now they’re home,” said Gary Abbott, director of communications for USA Wrestling, the amateur sport’s governing body. “Just like it will be at the Olympics.”
At Olympic Park this week, Luciana Silva, a tourist from Portugal, said she was unsurprised that mention of the Zika virus was not included in the informational exhibits recently installed there. “It’s a new worry for that part of the world, and it’s dangerous,” Ms. Silva said. “But I think when the Olympics start, it will be under control.”
Others like Mr. Polley had similar attitudes but nonetheless saw the late-stage challenges as significant. “Certainly if I was involved in running these Games,” he said, “I’d be very worried.”
Mr. Bach conveyed little worry on Wednesday. When asked about ticket sales, he said he had “no concern at all” because of cultural norms in Brazil. “Brazilians,” he said, “they do not buy tickets at such an early stage as the British are doing or Germans will do.”